Conventional wiring boards for mounting electronic components such as semiconductor devices and crystal oscillators are formed by, for example, disposing a wiring conductor comprising a metallized conductor containing a metal powder such as tungsten or molybdenum on a surface of an insulating base body made of an electrically insulating material such as an aluminum oxide sintered body.
Such a wiring board usually includes an electronic component mounting region provided with wiring conductors drawn to the surface so as to be connected to an electronic component. An electronic component is mounted on the electronic component mounting region of such a wiring board, each electrode of the electronic component is electrically connected to the corresponding one of the wiring conductors via electrically connecting means such as solder or a bonding wire, and a lid member made of a metal, ceramics, glass, a resin or the like is bonded such that the lid member covers the electronic component so as to seal the electronic component. An electronic apparatus is produced in this manner.
The lid member is bonded to the wiring board by, for example, using a sealant such as a resin. With the trend toward smaller electronic apparatuses, the width of a region in which the wiring board and the lid member are bonded is decreasing, and demand is growing for increased bonding strength between the wiring board and the lid member. For example, in order to increase the bonding strength between the wiring board and the lid member, a wiring board having a recess portion on the upper face thereof is known in which in a frame-like portion (side wall portion) surrounding the recess portion, a groove having a V-shaped cross section (with its opening width being as large as the width of the side wall portion) is formed so as to extend over the entire width of the side wall portion from the outer end to the inner end (see, for example, Patent Literature 1).
Also, the size of wiring boards is decreasing with the recent growing demand for smaller electronic apparatuses. In order to efficiently produce a plurality of wiring boards having a reduced size, a technique is performed in which a plurality of wiring boards are produced by dividing a multiple patterning wiring board. The multiple patterning wiring board is a board in which a plurality of wiring board regions are arranged and formed in rows and columns in a center portion of a broad base substrate, the wiring board regions each serving as a wiring board after the base substrate is divided, and dividing grooves for dividing the wiring board regions are formed in rows and columns. By bending the base substrate to separate the individual wiring board regions along the dividing grooves, a plurality of wiring boards are obtained.
Some wiring boards are flat plate-shaped without a recess portion, and a lid member that has a recess portion and covers an electronic component mounted on the center portion of the wiring board is bonded to such a wiring board. In this case, in order to increase the bonding strength between the wiring board and the lid member, a method can be conceived in which, as in the case of the wiring board having a recess portion as described above, a groove having a V-shaped cross section (with its opening width being as large as a width between the electronic component mounting region and an outer edge of the wiring board) is formed so as to extend over the entire width between the electronic component mounting region and the outer edge of the wiring board.